Wireless communication devices, such as mobile devices and base stations, include signal processing functions that bridge the processing of one or more signals at baseband with the processing of the one or more signals at radio frequencies. These signal processing functions may be embedded in a so called digital front-end (DFE). The digital front-end may include a so-called channelization device, at least a sample rate conversion block and a digitization block. The channelization device can convert the one or more carrier signals from the baseband into radio frequency (RF), e.g. in a transmitter. Alternatively, the channelization device may convert the one or more carrier signals from RF to the baseband, e.g. in a receiver. Typically the channelization device also performs filtering, e.g. removal of adjacent channels interferers. The sample rate conversion block may convert a fixed clock rate into a target rate of a respective air interface, e.g. in a receiver. Alternatively, the sample rate conversion block may convert a target rate of a respective air interface into a fixed clock rate, e.g. in a transmitter.
Wireless communication devices also include transmitter and/or receiver circuits (i.e., transceivers) in which power amplifiers are used to amplify a signal before wireless transmission to another device. For example, base stations employing wideband digital communication transmitters will constructively add a plurality of carrier signals, resulting in multi-carrier signals each having a large peak-to-average power ratio (PAPR) which can adversely constrain the performance of high power amplifiers used to amplify the multi-carrier signal for transmission. Such high power amplifiers can be very expensive and need to be efficient. Efficiency of a power amplifier improves at saturation for maximum output power levels. However, at maximum output power levels, linearity of the power amplifier is reduced. It is therefore preferred to operate the power amplifiers with signals whose maximum possible instantaneous peak amplitude keeps the power amplifier in the linear range. Reducing the peak-to-average power ratio of the signals handled by the power amplifier produces a signal having a higher total average power (the total average power of the signal is given by its peak power divided by the PAPR), thereby keeping the power amplifier efficient and in the linear range.
In order to reduce the PAPR in wireless communication devices, a series of operations are required in digital front-ends to provide signals to the power amplifier with the desired PAPR. These operations include pulse shaping, crest factor reduction, carrier aggregation, interpolation, and require a significant amount of computational resources.